The audio file summarizes receptors and signal transduction, focusing on G-protein coupled receptors. It discusses the structure of GPCRs, how they interact with G-proteins and effector enzymes to produce second messengers. A classic example of epinephrine signaling through a GPCR is described, from receptor binding through second messenger production and effects on target proteins and cell activity. Methods for demonstrating cAMP release of PKA catalytic subunits in vivo, such as using fluorescent proteins and FRET, are also summarized.

1. Audio file recorded on previously
to cover for missed class on
Wednesday October 24, 2012

2. Receptors and Signal Transduction
• Defining receptors and signal transduction
• Examples of receptor types
• Receptor characteristics
• Measuring receptor activity

3. G-protein coupled receptors

4. G-protein coupled receptors
• Receptor tertiary structure is conserved
– Serpentine
• Receptor interacts with G-protein as
transducer protein
• Effector enzyme generally produces 2nd
messengers

5. Cell activity can
change in response
to external signals
1. Signal release
2. Signal binding
3. Transmission of information
across a membrane
4. Protein-protein transmission
5. Second messenger synthesis
6. Second messenger initiates
signaling pathway
7. Activated signaling pathway
8. Activated target protein
9. Changes in cell activity

6. Generic three dimensional structure
of a receptor that acts through a G-
protein: Serpentine receptor
Orange G-protein
binding domain
Red-phosphorylation
domain

7. G-protein coupled receptors
(serpentine receptors) produce
second messengers
Examples of second messengers

8. Epinephrine signaling is a classic example
of a G-protein mediated pathway
• Receptor: -adrenergic
• Transducer: G protein
• Effector:Adenylate cyclase
• Second messenger target: Protein kinase A
• Physiological targets:
– Sugar and lipid metabolism
– Respiration and heart rate

9. What is epinephrine?

10. -adrenergic pathway: Epinephrine
signaling: (Adrenaline)

11. Heterotrimer G-proteins cycle through
active and inactive forms

12. -adrenergic pathway: Epinephrine
signaling: (Adrenaline)

13. Binding of cAMP
to Protein kinase
A leads to release
of regulatory
subunits activity
the kinase

14. Crystal structure of Protein kinase A

15. Holding these complexes in the
membrane requires A kinase
anchoring proteins

17. Heterotrimer G-proteins cycle through
active and inactive forms
Gilman and Rodbell
Nobel Prize in
Physiology and Medicine,
1994

18. Additional protein factors regulate
the activity of G proteins

19. G proteins can be locked in active
states by toxins

20. -adrenergic pathway: Epinephrine
signaling: (Adrenaline)

21. Binding of cAMP
to Protein kinase
A leads to release
of regulatory
subunits activity
the kinase

22. -adrenergic pathway: Epinephrine
signaling: (Adrenaline)

23. How can we demonstrate
that cAMP releases the
catalytic subunits in vivo?
GFP and other fluorescent proteins combined with FRET
2008 Nobel Prize
in Chemistry for
GFP
Marty Chalfie
Osamu Shimomura
Roger Tsien

24. Wavelengths of fluorescent protein
emission

25. Fluorescence resonance energy
transfer (FRET)

26. Demonstration
of release of
catalytic
subunits by
cAMP binding

27. FRET can also be used to measure
PKA activity in a living cell

28. Binding of cAMP
to Protein kinase
A leads to release
of regulatory
subunits activity
the kinase